javaweb返回json对象

1.准备

　　json-lib-2.4-jdk15:这个第三方jar包(版本随便,这里版本是2.4)

　　此外还需要额外json-lib所依赖的包json-lib-2.4-jdk15.jar所需全部JAR包.rar

2.设置头部

    req.setCharacterEncoding("utf-8");
    resp.setCharacterEncoding("utf-8");
    resp.setHeader("content-type", "application/json;charset=utf-8");
    PrintWriter pw = resp.getWriter();
    JSONObject jo = new JSONObject();
    jo.put("status", 200);
    jo.put("msg", "访问成功");
    pw.write(jo.toString());